DEVELOPMENT OF SELF-CURING CONCRETE USING POLYETHYLENE GLYCOL AS INTERNAL CURING AGENT

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1 International Journal of Civil Engineering and Technology (IJCIET) Volume 9, Issue 7, July 2018, pp , Article ID: IJCIET_09_07_119 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indeed DEVEOPMENT OF SEF-CURING CONCRETE USING POYETHYENE GYCO AS INTERNA CURING AGENT M V Jagannadha Kumar Research Scholar in Civil Engineering, JNTUH CEH K Jagannadha Rao Professor of Civil Engineering, CBIT, Hyderabad B Dean Kumar Professor of Civil Engineering, JNTUH CEH, Hyderabad V Srinivasa Reddy Professor of Civil Engineering, GRIET, Hyderabad ABSTRACT Self-curing or internal curing is a process in which moisture present in the concrete is preserved for more effective hydration of cement and reduced self-desiccation. In this paper, Self-curing concrete of M20, M40 and M60 grades are developed using optimized dosage of polyethylene glycol as internal curing agent. Compressive, splittensile and fleural strength properties of self-curing concrete mies are evaluated and ehaustive cost analysis is made on internally and eternally cured concrete for economic feasibility. The optimum dosage of polyethylene glycol (PEG) (epressed in percentage by weight of cement) for M20, M40 and M60 grades self-curing concrete are 1%, 0.5% and 0.5% respectively. There is a significant increase of about 5-20% in the compressive, split-tensile and fleural strength properties of self-curing concrete mies when compared to normal eternally cured concrete mies for all the grades considered for study. This improvement may be attributed to the continuation of the hydration process as a result of continuous availability of water. This resulting in, lower voids and pores, and greater bond force between the cement paste and. It was found that there is significant cost saving ranging from Rs per cubic meter of concrete if internally cured. Key words: Self-Curing, Internal Curing, Polyethylene Glycol, Self- Desiccation, Cost Analysis editor@iaeme.com

2 M V Jagannadha Kumar, K Jagannadha Rao, B Dean Kumar and V Srinivasa Reddy Cite this Article: M V Jagannadha Kumar, K Jagannadha Rao, B Dean Kumar and V Srinivasa Reddy, Development of Self-Curing Using Polyethylene Glycol as Internal Curing Agent, International Journal of Civil Engineering and Technology, 9(7), 2018, pp INTRODUCTION Self-curing referred as Internal-Curing is a process of controlling the moisture loss from the concrete. curing methods are basically divided into two groups i.e. Water adding method and Water retaining method. The internal-curing technique is a part of water retaining method. There are two major methods available for internal curing of concrete. The first method uses saturated porous lightweight (WA) to supply an internal source of water, which can replace the water consumed by chemical shrinkage during cement hydration. The second method uses hydrophilic materials in concrete which reduces the evaporation of water from the surface of concrete and also helps in water retention. In the present study, the second method is adopted. The use of hydrophilic materials in concrete controls the loss of water and also attracts moisture from the atmosphere which provides continuous curing to concrete. Some special type of materials used in the internal curing process are ightweight Aggregate (WA) (natural and synthetic, epanded shale), Super-absorbent Polymers (SAP) and SRA (Shrinkage Reducing Admiture) i.e., propylene glycol, polyvinyl alcohol, Paraffin Wa, Acrylic acid. Miing water itself cannot help in complete hydration of cement paste whereas internal curing can provide the required amount of water for complete hydration and to maintain the high relative humidity (RH) which prevents self-desiccation. This mechanism produces hard, dense concrete and minimizes shrinkage cracking, thermal cracking. 2. PROBEM STATEMENT Proper curing of concrete structures is vital to meet performance and durability requirements. Curing allows incessant hydration of cement and subsequently continuous gain in the strength. ack of proper moisture conditions virtually slows down the hydration of the cement. Hydration practically stops when the relative humidity within the pores falls below 80%. The conventional curing is achieved by eternal applied water after hardening of concrete. Self-curing or internal curing is a process of preserving moisture in concrete for more effective hydration of cement and reduction of self-desiccation [1]. When concrete is eposed to the arid environment, evaporation of water takes place therefore loss of moisture will reduce the initial water- cement ratio which will result in the incomplete hydration of the cement affecting the quality of the concrete. Evaporation in the initial stage leads to plastic shrinkage cracking and at the final stage of setting it leads to drying shrinkage cracking. So curing period and temperature are very important factors that affect the strength development rate [2]. At high temperatures, ordinary concrete loses its strength due to the formation of the cracks between two thermally incompatible ingredients, i.e., cement paste and s. Continuous evaporation of moisture takes place from an eposed surface due to the difference in chemical potentials between the vapour and liquid phases. The chemical polymers added into the mi as self-curing agents primarily form hydrogen bonds with water molecules and reduce the chemical potential of the water molecules which in turn reduces the vapor pressure subsequently reducing the rate of evaporation from the surface. The mechanism of internal curing is to hold the preserved water content of concrete structures so that they do not require any additional water for curing purpose. It is found that one cubic meter of finished concrete requires about three cubic metre of curing water [3]. Providing water for eternal curing has some limitations such as availability of good quality water, lack of accessibility of the structure, limited water cement ratio used in editor@iaeme.com

3 Development of Self-Curing Using Polyethylene Glycol as Internal Curing Agent high performance concrete. To counter the above concerns, internal curing is the most appropriate solution. When polyethylene glycol (PEG) is added to water it forms hydrogen bonds which reduces water evaporation from concrete subsequently increasing the cement hydration. Rate of hydration increases the amount of solid phase of the paste as water is consumed by chemical reactions of hydration. In addition, water adsorbed onto the surfaces of the solids in the hydration products keeps them saturated maintaining the relative humidity in the paste to evade the phenomenon of self-desiccation. When the relative humidity drops below 80 %, the hydration rate slows down and it becomes negligible when the internal relative humidity drops to 30 % [4]. 3. PROJECT SIGNIFICANCE In the present paper, Self-curing concrete of M20, M40 and M60 grades are developed using optimized dosage of polyethylene glycol as internal curing agent. Workability, water retention capacity, compressive, split-tensile and fleural strength properties of self-curing concrete mies are evaluated and ehaustive cost analysis is made on internally and eternally cured concrete. The effect of internal curing initiates immediately with the initial hydration of the cement, so that its benefits are witnessed at ages as early as 2 or 3 days [5].Internal curing is advantageous in low water cement ratio (w/c) concretes because of the chemical shrinkage during hydration and its low permeability. Since the water incorporated into and adsorbed by the cement hydration products has a specific volume less than that of bulk water, a hydrating cement paste will imbibe water (about 0.07gmof water/1gmof cement) from available sources[6].while in higher w/c concretes, this water is often supplied by eternal (or surface) curing. In low w/c concretes, the permeability of the concrete is too low to allow the effective transfer of water from the eternal surface to the interior of concrete [7]. This is the major reason to justify the need for internal curing. If water can be dispersed uniformly throughout the concrete, it will be readily available to migrate to the surrounding cement paste and contribute for the hydration process as required. From the review of literature it is found that the influence of molecular weight and dosage of self-curing agents was not given due significance to study the efficiency of self-curing. This paper focusses on determination of the optimum dosage and the molecular weight of PEG to accomplish efficient self-curing of concrete by studying the water retention by loss /or gain of weight of the specimens. Manufacturing cost of eternally cured and internally cured concrete mies of various grades are also estimated to understand the economic viability. 4 MATERIAS AND MIX PROPORTIONS 4.1. Polyethylene Glycol In this project, after several trials, Polyethylene glycol (PEG) of molecular weight 400 is chosen as self-curing agent. Polyethylene-glycol is a condensation polymer of ethylene oide and water with the general formula H(OCH2CH2) noh, where n is the average number of repeating o ethylene groups typically from 4 to about 180 [8].Polyethylene glycol 400 is strongly hydrophilic. After trials, it was found that polyethylene glycol (PEG) of lower molecular weight i.e., PEG 400 is more efficient as a self-curing agent when compared to the PEG of higher molecular weight. Increasing the molecular weight of polyethylene glycol also results in decreasing solubility in water [9] and also past literature reported that hygroscopic capacity decreases as molecular weight increases [10]. Table 1 shows the properties of PEG 400. Table 2 presents the quantities per cu.m. for various grades of concrete editor@iaeme.com

4 M V Jagannadha Kumar, K Jagannadha Rao, B Dean Kumar and V Srinivasa Reddy Cement kg Table 1 Properties of PEG 400(Source: Property Name Property Value Specific gravity 1.12 at 27 ο C ph >6 Molecular weight (gm/mol) 400 Appearance Clear liquid Colour White Hydroyl value ( mg KOH/gm) 300 Nature Water soluble Molecular formula H(OCH 2CH 2) n OH Density g/cm Table 2 Quantities per cu.m. for various grades of concrete Microsilica Fine kg Coarse kg Water Super plasticizer Polyethylene Glycol (PEG) M M M (6% b.w.c) b.w.c by weight of cement 5. RESEARCH FINDINGS This section presents test results of various eperimental investigations carried out on various grades of normal cured and self-curing concrete mies Workability Table 3 presents workability of various grades of concrete mies incorporated with various dosages of Polyethylene Glycol (PEG 400). Table 3 Workability of various grades of concrete mies incorporated with various dosages of Polyethylene Glycol (PEG 400) Polyethylene Glycol (PEG) Dosage (Percentage by weight of cement) Slump in mm M20 M40 M60 0 % % % % % Table 4 presents the compressive strengths of various grades of concrete mies incorporated with various dosages of Polyethylene Glycol (PEG 400) at 28 days age of curing. Table 4 Compressive strengths of self-curing concrete mies made with various dosages of Polyethylene Glycol (PEG 400) Polyethylene Glycol (PEG) Compressive Strength at 28 days age of curing Dosage (Percentage by weight of cement) M20 M40 M60 0 % ( eternal curing) % % % % editor@iaeme.com

5 Development of Self-Curing Using Polyethylene Glycol as Internal Curing Agent Figure 1 shows the optimum dosage of polyethylene glycol (PEG) (epressed in percentage by weight of cement) to be used in various grades of self-curing concrete. Figure 1 Optimum dosage of polyethylene glycol (PEG) Table 5presents the Compressive, Split-tensile and Fleural strength properties of normal and self-curing concrete mies at various ages of curing. Table 5 Compressive, Split-tensile and Fleural strength properties of normal and self-curing concrete mies at various ages of curing. Type Normal (Water cured) Self-curing (Air cured) Property Compressive Strength Split Tensile Strength Fleural Strength Compressive Strength Split Tensile Strength Fleural Strength Age of Curing Grade of the concrete days days days days days M M M M M M M M M M M M M M M M M M COST ANAYSIS Manufacture cost of Normal concrete mies in Rupees per cu.m is presented in Table 6. Total cost incurred for Normal (eternally cured) concrete in Rupees per cu.m.is presented in Table 7.Manufacture cost of Self-curing (Internally cured) concrete mies in Rupees per cu.m. is presented in Table 8. Table 9 compares the rate incurred for eternally and internally cured concrete mies in Rupees per cu.m editor@iaeme.com

6 M V Jagannadha Kumar, K Jagannadha Rao, B Dean Kumar and V Srinivasa Reddy For eternal curing it was estimated that for one cu.m. of concrete at least 3 cu.m or 3000 itres water is required. Time of application of water eternally is about 8hr/day for 7 days continuously at Rs.400 per day as abor charges. Costs of materials are assumed based on market prices as follows: 1. Cement Rs 6/kg; 2. Microsilica Rs 22/kg; 3. Fine Rs 1.8/kg and Coarse - Rs 0.70/kg; 4. Water- Rs 0.50/; 5. Super plasticizer- Rs 40/kg; 6. Polyethylene Glycol (PEG 400)- Rs.544/ Table 6 Manufacture cost of normal concrete mies (Rs. per cu.m) Grade of M20 M40 M60 Cement (a) kg Rs kg Rs kg Rs Microsilica (b) kg Rs Fine (c) kg Rs kg Rs kg Rs Coarse (d) kg Rs kg Rs kg Rs Water (e) 173 Rs Rs Rs Rs Super plasticizer (f) Cost / cu.m. (a)+(b)+(c)+ (d)+(e)+(f) - Rs Rs Rs.40 Rs Rs Grade of M20 M40 M60 Table 7Total Cost of Normal (Eternally Cured) per cu.m. Cost of per cu.m (a) Rs Rs Rs Cost of Water required for eternal curing of one cu/m. of concrete (b) 3000 Rs Rs Rs.1500 Cost of Etra labor required to apply the water eternally (c) Total cost incurred for eternally cured per cu.m. (a)+(b)+(c) Rs Rs Rs editor@iaeme.com

7 Development of Self-Curing Using Polyethylene Glycol as Internal Curing Agent Table 8 Total Cost of Self-curing (Internally cured) concrete mies (Rs. per cu.m) Cement (a) Microsilica (b) Fine (c) Coarse kg (d) Water (e) PEG (f) Super plasticizer (g) Cost / cu.m. (a)+(b)+ (c)+(d)+ (e)+(f)+(g) M kg Rs kg Rs kg Rs Rs Rs Rs.544 Rs Rs M kg Rs kg Rs kg Rs Rs Rs Rs.544 Rs Rs M kg Rs kg Rs kg Rs kg Rs Rs.544 Rs Rs.40 Rs Figure 2 Cost comparison of eternally and internally cured concrete per cu.m editor@iaeme.com

8 M V Jagannadha Kumar, K Jagannadha Rao, B Dean Kumar and V Srinivasa Reddy Table 9 Cost comparison of eternally and internally cured concrete per cu.m. Cost of normal ( Eternal Curing) per cu.m Cost of self-curing agent (PEG 400) incorporated ( Internal Curing) per cu.m Cost Saving M20 Rs Rs Rs M40 Rs Rs Rs M60 Rs Rs DISCUSSIONS In the present study, M20, M40 and M60 grades of eternal water cured normal concrete specimens and air cured self-curing concrete specimens using optimized dosage of polyethylene glycol as internal curing agent are developed. It is observed that as grade increases workability decreases in self-curing concrete mies. Similarly as dosage of polyethylene glycol (PEG) increases, workability increased. The optimum dosage of polyethylene glycol (PEG) (epressed in percentage by weight of cement) for M20, M40 and M60 grades self-curing concrete are 1%, 0.5% and 0.5% respectively. There is a significant increase in the compressive, split-tensile and fleural strength properties of self-curing concrete mies at all ages of curing when compared to normal eternally cured concrete mies of about 5-20% for the grades considered in this study. This improvement may be attributed to the continuation of the hydration process as a result of continuous availability of water resulting in, lower voids and pores, and greater bond force between the cement paste and as stated in the previous literature. It is understood that, the role of self-curing agent polyethylene glycol is to reduce water evaporation from concrete, hence there is an increase in the water retention capacity of self cured concrete, when compared with normal concrete, which leads to enhanced compressive strength. This improvement in strength is not only due to the ability of concrete to retain water which causes continuation of the cement hydration, but also due to the conversion of calcium hydroide into CSH. This CSH formed on the surface of particles strengthens the -matri transition zone which becomes less porous and more compact. The research findings of past researchers demonstrated that the PEG is affecting the bond between the particles and the cement paste. The region between the cement paste and particles is usually populated by massive crystals of CH, and it is generally believed that the nature of these crystals influences the strength of the cement paste- bond, which in turn affects the strength of the concrete as a whole. It has been previously reported by other researchers that the addition of the PEG has the effect of altering the morphology of CH in cement pastes. There is evidence from past literature that the PEG is altering CSH gel morphology. This appears to enhance the nature of the CSH gel, leading to better permeability characteristics. ow dosage of polyethylene glycol is more efficient for achieving self-curing concrete when compared to the higher dosages. Polyethylene glycol of lower molecular weight is found to be more efficient as a self-curing agent when compared to the PEG of higher molecular weight. In practice, for actual site conditions, the conventional concrete requires water for eternal curing as well as an etra labor to apply the water to the concrete for a minimum duration of 7days at 8hr/day whereas with the development of internally cured concrete the amount of water applied for eternal curing and its labor cost can be saved as there is no such requirement of curing in case of internal cured concrete. So an attempt was also made to find out the rates and editor@iaeme.com

9 Development of Self-Curing Using Polyethylene Glycol as Internal Curing Agent compare the cost incurred for the normal concrete and internal cured concrete. It was found that there is significant cost saving ranging from Rs per cubic metre of concrete if concrete is internally cured. 8. CONCUSIONS From the results obtained in this study the following conclusions can be noted: The use of self-curing agent (polyethylene glycol) in concrete mies improves the strength properties of concretes under air curing regime which may be attributed to a better water retention and causes continuation of the hydration process of cement past resulting in less voids and pores, and greater bond force between the cement paste and. It is observed that as grade increases workability decreases in self-curing concrete mies. Similarly as dosage of polyethylene glycol (PEG) increases, workability increased. The optimum dosage of polyethylene glycol (PEG) (epressed in percentage by weight of cement) for M20, M40 and M60 grades self-curing concrete are 1%, 0.5% and 0.5% respectively. There is a significant increase in the compressive, split-tensile and fleural strength properties self-curing concrete mies at all ages of curing when compared to normal eternally cured concrete mies. It was found that there is significant cost saving ranging from Rs per cubic metre of concrete if concrete is internally cured. REFERENCES [1] A Francis,J John, (2013), Eperimental Investigation On Mechanical Properties Of Self- Curing, International Journal of Emerging Vol.2,Issue3, pp [2] D P Bentz, P ura, J W Roberts, (2005) Miture proportioning for internal curing, International (27), pp [3] Dhir R K, Hewlett P C, ota, J S, and Dyer T D(1996), Influence of Microstructure on the Physical properties of Self-Curing, ACI Materials Journal, Vol.93 (5), pp [4] J Castro, Keiser, M Golias, J Weiss, (2011), Absorption and desorption properties of lightweight for application to internally cured concrete mitures, Cement Composites (33), pp [5] K Vedhsakthi, M Saravanan- (2014), Development of normal and high strength self-curing concrete using SAP and comparison of strength characteristics, International Journal of Engineering Research & Technology (IJERT) volume: 03 Issue 10 Oct [6] Ole Mejlhede Jensen and Pietroura (2006), Techniques and materials for internal water curing of concrete, Materials and Structures, Vol.39, pp , [7] Pietroura and Ole Mejlhede Jensen (2007), Eperimental observation of internal water curing of concrete, Materials and Structures. Vol.40, pp , [8] R K Dhir, P C Hewlett, J S ota, T DDyre (1994), An investigation into the feasibility of formulating self-curing concrete, Materials and Structures. 27 (1994) pp [9] S Zhutovsky, KKovler (2012), Effect of internal curing on durability related properties of high performance concrete, Cement and Research (42) (2012) [10] Weber S, Reinhardt H W (1996), Various curing method applied to high-performance concrete with natural and blended s, In: Proceedings of Fourth International Symposium on the Utilization of high Strength/High Performance concrete, Paris, May 29, pp editor@iaeme.com